Refrigerating apparatus



July 1, 1930. I F. w. ANDREWS REFRIGERATING APPARATUS 2 Sheets-Sheet 1Filed Feb. 28, 1927 July 1, 1930; w ANDREWS 7 1,768,557

REFRIGERATING APPARATUS- F'iled Feb. 28, 1927 2 Sheets-Sheet 2 To Cornresorfrom Eur va n r Ju 46 QWWMW 3% $5 Wz/M atto'cmgl sure in thelow-pressure side of I pressor Patented July 1, 1930 FRANK W. ANDREWS;0F DAYTON, OHIO, FRIGIDAIRE CORPORATION, A

ASSIGNOR, BY *MESNE ASSIGNMENTS, IO CORPORATION' OF DELAWAREREFRIGERATING APIEARATUS Application filed February 28, 1927. Serial No.171,486.

This invention relates to refrigerating ap- I paratus of thecompressor-condenser-expander type controlled automatically in responseto a refrigerating demand.

It is among the objects of the invention to improve the apparatus forcontrolling such a system, to make the system more reliable inoperation, and to reduce the power required to operate it. Morespecifically it is an object to provide a system in which the control isoperated in response to the presthe system and which has means forreventing operation of the control when there is no refrigeratingdemand. 7

Further objects and advantages ofthe present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein a preferred form of the present invention is clearlyshown.

In the drawings Fig. 1 is a diagram of a refrigerating system embodyingmy invention, an

Fig. 2 is a section of a control valve drawn on an enlarged scale.

The system shown in the drawings includes a compressor 10 and a circuitfor refrigerant including a high pressure con- .duit 11, condenser 12,receiver 13, expander 14, and low-pressure conduit 15. The comis drivenby any suitable sourceof power, such as a motor 16, started and stoppedby a switch 17, which is opened and closed by a pressure responsivedevice 18 connected to the low-pressure conduit at 19.

When refrigeration is required, the expander is warm, and relativelyhigh pressure exists in the expander and low-pressure conduit 15. Thismoves the pressure responsive switch to start the motor and drive thecompressor to circulate refrigerant, which evaporates in the expander toproduce refrigeration in' the well-known manner. "When I suflicientrefrigeration has been produced, the expander is' cold and the pressureexisting in the expander and in the low-pressure conduit isrelatively-low. This permits the pressure responsive device to collapseand open the switch, stopping' the motor.

Thecompressor includes a cylinder 20, piston 21 and crankcase 22 havingan inlet 23. The cylinder has a discharge check valve '24: and thepiston has an intake valve 25.

On the down stroke the piston travels against the pressure of gas in thecrankcase, and the piston valve 25 opens, permitting gas to flow intothe cylinder, while on the up stroke this valve closes and the gas iscompressed and pushed out through check valve 2 1.

In the system thus far described, two difficulties have beenencountered. First, due to leaks in the check valve, the system mayoperate when there is no refrigerating de- 6 mand. In production it isvery difficult to make a check valve which will not leak to a smallextent. It has been found that even a very slight leak will allowrefrigerant to pass from the high-pressure side of the system .backthrough the compressor into the low-pressureconduit 15 and evaporator 14when the compressor is idle, thus building up pressure in thelow-pressure side when the evaporator is cold and no refrigeration isrequired. This pressure will, of course, in time operate the switch tostart the motor. Secondly, the power required to start the compressormay be excessive. If, forany reason, the power should be disconnectedfor any-appreciable time, as when shipping or storing the apparatus, thecheck valve may leak enough to equalize the pressure in conduits 11and'15. This builds up pressurein the low-pressure side, which mayevenbe of the order of fifteen times its normal operating value. Then, whenthe compressor is started. the piston must travel against an excessivepressure, which puts additional load on the motor. Usually many strokesof the piston against this heavy load are required on starting, becausein practice the volume of the low-pressure side, including crankcase,conduit, and evaporator is many times .the piston displacement.Therefore, i

such an apparatus requires a large motor with high starting torque tomeet these conditions.

In order to avoid the difliculties above mentioned, I place a shut-offvalve 28, shown ing at its edges-in'any suitable manner, such .close ata pressure,v

in the crankcase,

--in the low-pressure side ounces until it has been as being clampedbetween the housing 29 and another housing 34 by bolts 35. The inlet 32is provided with a valve seat 36 which co-operates with the valve 37 toclose the conduit. The valve 37 is attached to a stem 38 suitablysecured to the diaphragm and urged to open position by a spring 39placed between a collar 40 and a bushing 41 threaded into the upper endof the housing 34. The pressure within the chamber 30 acting on thediaphragm, tends to close the valve against the force of the spring. Thespring tension may be adjusted by screwing the bushing 41 in or out. Ialso provide a thumb nut 42 threaded on the upper end of the stem andadapted to engage the upper end of the bushing for positively closingthe valve 37 and holding it closed when desired, as when shipping arefrigerating unit. A spring 43 serves to prevent this nut fromrattling, due to vibrations of the compressor, when operating.

Operation The automatic switch 17 may be set to for example, of 2 poundsper square inch and to open at a vacuum of 8 inches of mercury. Theupper side of the diaphragm'in the shut-off valve may be exposed to thepressure of the atmosphere, and by suitably proportioning the area ofthe diaphragm, tension of the spring, and the length of the valve stem,the valve may be set to close at any desired pressure--- between theoperating-limits of the pressure switch. For example, it may be set toclose at a pressure of 6 ounces per square inch above atmosphere.Consequently if the compressor and check valve should leak, as soon as apressure of 6 ounces has been established low-pressure conduit andexpander, the valve 37 will be closed and be held closed. Furtherleaking of the check valve may build up the pressure in the crankcase tothe pressure existing in the gh-pressure side of the system which mayfor example, pounds per square inch, but this pressure can not beestablished in the conduit and expander, and the pressure will remain at6 increased by the the motor on starting circuit for warming up of theevaporator. It will thus be seen that the pressure existing in thelowpressure conduit is a true indication of the refrigerating demand andthe switch can not start the motor unless there is such demand.

While the pressure in the crank-case'under the conditions just supposedmay be as high as 70 pounds, the volume of gas at this pressure whichmust be moved by the piston on starting is limited to the capacity ofthe crankcase. This is all removed by relativelyfew strokes of thepiston, whereas if the pressure had been allowed to build up in theconduit 15 an evaporator 14, a great many more strokes of the pistonwould be requlred to reduce the pressure. Since the high pressure in thecrankcase continues for only a few strokes of the piston, a highstarting torque is required only for a very brief space of time. Thismaterially reduces the amount of power required to drive and permits asmall motor to be used.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. Refrigerating apparatus comprising a circuit for refrigerant,including a normally open low-pressure conduit, a pump for circulatingrefrigerant in the circuit, means responsive to the pressure in theconduit for actuating the pump and means positively preventing theoperation of, the actuating means in response to pressure existing inthe P P- 2. Refrigerating apparatus comprislng a circuit forrefrigerant, includin a low; pressure conduit, a pump for circulatingrefrigerant in'the conduit, means connected to the conduit for actuatingthe pump in response to pressure within the conduit and means forautomatically closing the conduit between the pump and point ofconnection of the actuating means when the pressure in the conduitexceeds a predetermined amount. 7

3. Refrigerating apparatus comprising a circuit for refrigerantincluding a normally open low-pressure conduit, a pump for circulatingrefrigerant inthe circuit, means connected to the conduit for actuatingthe pump when the pressure in the conduit is above a predeterminedamount, and means positively preventing high pressure existing 1n thepumpfrom being communicated to the conduit. Y

4. Refrigerating apparatus comprising a refrigerant including alow-press'ure conduit, a pump-for circulating refrigerant in thecircuit, means fordriving the pump, means for actuating the driving andthefpump for closing.

insets means including a pressure-responsive device connected t o theconduit, and a pres sure-responsive value between said devlce theconduit when the pressure exceeds a predetermined amount.

' 5. Refrigerating apparatus circuit for refrigerant including anexpander and a low-pressure conduit, one end of which is connected to.the expander, a pump connected to the other end of the conduit forcirculating refrigerant in the circuit, means connected tot he conduitintermediate its ends for actuating the pump in response to the pressurein the conduit, the conduit being always open atv the expander end, and

the

means for closing the pump end of conduit when the pressure in theconduit exceeds a predetermined amount.

In testimony whereof I hereto aflix my signature.

FRANK w. ANDREWS.

comprising a

